[CentOS-docs] Notes on HowTos/Custom Kernel

Thu Oct 2 18:07:48 UTC 2008
Filipe Brandenburger <filbranden at gmail.com>

Hi Akemi,

On Thu, Oct 2, 2008 at 13:04, Akemi Yagi <amyagi at gmail.com> wrote:
> Because we do not include the vanilla kernel and
> are staying withing the CentOS distro kernel in that wiki
> instructions, I'm not sure whether we should refer to the cplus
> kernel.  It is a great product offered by Mr. Hughes, but it is a
> custom kernel per se.  But if you feel adding notes that pertain to
> the cplus kernel makes the wiki article a better one, I would be
> willing to do it.

Actually, as you can probably see in my recent post to the CentOS
list, I had to create a custom kernel to support a specific hardware
that I had. I also needed XFS, that's why I did it over the CentOS
Plus kernel.

It was not that hard to do it based on the original instructions, but
there are some differences. For example, the snippet that starts at
line 4779, the one that starts with "#if a rhel kernel, apply the rhel
config options", that one is not present at all on the CentOS kernel,
but I just went ahead and it worked fine. At the end, although in some
places I had to make a choice on whether I followed the instructions
for the default kernel or not, I could successfully build it and it
worked, and it was not too hard (took me just 2 or 3 hours to do it).

What I think would be really great would be an explanation of why the
items in section "3. Modifying the kernel spec file" have to be done,
because knowing what does each of them do and why they have to be
commented would have helped me in choosing what I should and what I
should not do. Of course, that page by itself is a great guide, and
including lots of explanations of why this and why that would probably
be a lot of clutter there, but maybe a separate page with the
rationale would be very useful, especially when new kernels are
available (CentOS 6?) and the page will no longer work in terms of
following literal instructions.

Another thing that bit me yesterday is that I used a "buildid" for my
kernel, and then I could no longer load the XFS filesystem. I had to
rebuild the xfs-kmod RPM as well, in that case I had to use a special
rpmbuild command line so that it compiled it only for my arch, only
for the default kernel (not xen, etc.) and for that specific buildid.
I don't recall exactly which command line I used, and my build host
was reinstalled soon after that, but if you wish I could try to
reproduce that environment again in another machine to get it right
and post it here.

Thanks a lot! The documentation looked great already, it looks even
better now!!! :-D